Basic lead styphnate and process of making it



' ducing basic lead styphnate in these forms.

Patented Nov. 22, 1938 PATENT FF1E BASIC LEAD STYPHNATE AND PROCESS OFMAKING'IT vWilli Brun, Bridgeport, Conn, assignor to Remington'ArmsCompany, Inc., acorporation of Delaware No Drawing. ApplicationJune 2, 1933, Serial No. 674,049. Renewed February 11, '1937 5 Claims.

This invention relatesto the manufacture of styphnic-acid and certain ofits salts, and, contemplates improvements and refinements in theproduction ofv styphnic acid,.the practice of which results in a productadapted to. be. made into salts having certain desirable properties andcharacteristics. a ,-,More specifically-,the invention contemplates ,thecontrolofthe shape and form of, the crystals of certainsalts of styphnicacid, particularly basic lead styphnate, and certain methodsin themanufacture of styphnic 'acidwhich enable the acid to form salts havingnovel and desirable crystal shapes. 1 a V j The manufacture of basiclead styphnate and particularlyia red crystalline form thereof isdescribed in this applicants prior co-pending application, Serial No.569,835, filed October 19, 1931, Patent No. 1,942,274. It may be brieflysummarized as follows:

A solution of styphnic acid and sodium hydroxide, in the proportions of12.2 grams of styphnic acid and 8 grams of sodium hydroxide in 400 c. c.of water, is dropped into a lead nitrate solution of the concentrationof about 35 grams of lead nitrate in 350 c. c. of water. The temperatureis maintained between and C.,

and the styphnic acid-sodium hydroxide solution is at first dropped intothe lead nitrate solution very slowly. The first precipitate is apreviously known yellow amorphous or partly amorphous basic leadstyphnate which, if the sodium hydroxide-styphnic acid solution is atfirst introduced quite slowly, changes over to a heavier red crystallinebasic lead styphnate which quickly settles out.

When in the practice of the process above outlined ordinary styphnicacid is used, the crystals of basic lead styphnate are rather thickhexagonal plates. They are less fragile and sensitive to friction andshock than the previously known yellow needle crystals. The presentinvention comprises the discovery of other crystalline forms of basiclead styphnate, and methods for pro- The novel crystal shapes resultfrom the use of styphnic acid made in accordance with certain proceduresconstituting a part of the present invention. The manufacture ofordinary styphnic acid will first be briefly described:

The raw material is resorcine (CeH4(OI-I)2). By treatment withconcentrated sulphuric acid resorcine is sulphonated toresorcine-di-sulphonic acid, CsH2(OH)2(SO3H)2. Theresorcine-di-sulphonic acid is then nitrated with concentrated amountsof certain foreign substances.

nitric acid. The precipitated styphnic acid is separated from theresidue by centrifugal action or by filtration, and subsequently washedfirst with a dilute mineral acid andthen with water.

If the sulphonation of the resorcine is complete,

the resulting product is pure styphnic acid of a bright yellow color andlow gravimetric density,

from which crystalline salts are formed only with great difiiculty.

The present invention comprises the discovery that the character of thestyphnic acid may be altered in such a Way as to control the crystalshape of thesaltswhich it forms by the addition, during the operation ofsulphonating, of small 7 Such variations in the styphnic acid and in thecrystal shape of its salts, particularly the basic lead salt, areproduced by the use of any one of a number of different substances.Moreover, each substance has the property of producing its own Icharacteristic effects and crystal shape, each of these shapes differingfrom the others. For example, if to a batch comprising 110 grams ofresorcine and 460 c. c. of 98% sulphuric acid there be added 10 c. c. ofconcentrated nitric acid the resulting styphnic acid is darker in colorand less voluminous and its salts have different physical properties.The further addition of .1 gram of tri-oxy-methylene results in astyphnic acid which yields its basic lead salt in crystals'of a shapediffering very substantially from the usual crystals of this salt. Saidcrystals are somewhat elongated square or rectangular prisms, asdistinguished from the usual hexagonal plates, and appear to be moresensitive to shock and friction than the hexagonal plates. Two oppositefaces of the rectangular prismatic crystals appear to be substantiallysquare, while the other faces are tiallyrectangular cross section. Theaddition of c. c. of water produces an acid whose salt forms in crystalswhich are nearly cubical and exceptionally firm and dense. The additionof a small amount of aluminum produces salt crystals which are nearlycubical and unusually clean.

The use of sulphuric acid instead of 98% results in a mixture ofamorphous salt and comparatively short rectangular crystals. Acetic acidproduces a. striking effect in that the salt crystals are large shortrectangular prisms with rounded corners, somewhat resembling thecrystals of normal lead styphnate.

It should be remembered that the foreign substance is introduced in thesulphonation operation in the preparation of styphnic acid, and that thedescribed crystal shapes are those of the salts, particularly the basiclead salt of the acid produced in the presence of the foreign substance.

No satisfactory theoretical explanation of these effects can be offered.The foreign substances which cause them do not fall within anyrecognized class, or appear to have any property in common other thantheir ability to change the crystal shape of basic lead styphnate fromhexagonal to tetragonal. Among themselves their effects differ in thateach produces a crystal which is easily identified and distinguishedfrom the crystals produced by the others. Tri-oxymethylene, cathechol,glucose and aluminum, all tend to form oxides, hence should have areducing action. On the other hand, phenol and acetic acid are not suchreducing agents. Diluting the sulphuric acid and adding water tend tolimit'the amount of water that can be absorbed by the sulphuric acid,hence to lower the concentration of the nitrating nitric acid andincrease its oxidizing effect. Thus the general effect (production oftetragonal crystals) cannot be definitely attributed either to oxidationor reduction, nor is it limited to either organic or inorganic com-'pounds.

What is claimed is:

1. In the manufacture of salts of styphnic acid by the sulphonation andnitration of resorcine to styphnic acid and the subsequent formation ofa crystalline salt therefrom, the method of controlling the shape ofsaid salt crystals which comprises the addition during sulphonation oftrioxy-methylene.

2. In the manufacture of salts of styphnic acid by the sulphonation andnitration of resorcine to styphnic acid and the subsequent formation ofa crystalline salt therefrom, the method of controlling the shape ofsaid salt crystals which comprises the addition during sulphonation oftrioxy-methylene in the proportions of approximately .1 gram oftri-oxymethylene to grams of resorcine and 460 c. c. of concentratedsulphuric acid.

3. As a composition of matter, basic lead styphnate in the form oftetragonal prismatic crystals.

4. In the manufacture of basic lead styphnate by a process including thesulphonation and nitration of resorcine to styphnic acid and thesubsequent formation of a crystalline salt therefrom, the method offorming said basic lead styphnate in tetragonal prismatic crystals whichcomprises the addition during sulphonation of tri-oxy-methylene.

5. In the manufacture of salts of styphnic acid by a process comprisingthe sulphonation and nitration of resorcine to styphnic acid and thesubsequent formation of a crystalline salt therefrom, the method ofcontrolling the shape of said salt crystals which comprises the additionof trioxy-methylene during the preparation of said styphnic acid.

35 WILLI BRUN.

